(a) Field of the Invention
This invention relates to a modular optical imaging system. More specifically it relates to such a system in which a central element which carries an afocal variator optical system is provided, and to which central element both a front optical system and a rear optical system can be substantially permanently connected in combination to vary the actual focal length of the front optical system in conjunction with the rear optical system without the need to physically change the length dimension of any system, or without the need to change the lens position, or without the need to change lenses of the front or rear optical systems.
(b) Discussion of the Prior Art
"Varios" and "variators" are well known and useful optical systems. Such systems have found use primarily in zoom lens systems and in projectors, for example, to change the size of a projected image on a screen, but not to focus the image. In many instances, such vario and variator devices have been used, in combination with a front optical system or a rear optical system. In some instances they have even been used in combination with both a front optical system and a rear optical system. However, in all known instances such optical systems which incorporate vario and variator optical systems have been used to alter the size of an image but not to focus the image, and are used and usually only function at relatively short back focal distances.
Afocal variators of the specific type described in the present application have been known and in commercial use and on sale, by themselves, for at least fifteen years, for example for use in projector lenses to alter the size of a projected image on a screen. However, while afocal variator optical systems of the specific type disclosed herein, have been previously known in the art, such afocal variator optical systems are not known to have been previously used in the art to focus optical systems in the manner disclosed, provided and claimed by the present application, as opposed to the prior art use to alter image size at a fixed focal plane.
It is thus seen that while the use of varios and variators, either alone, or in combination with either a front optical system or a rear optical system are known, they are not known to have been used in combination with both a front optical system and a rear optical system to alter active focal length so as to act as a focusing system as opposed to a system for altering image size at a fixed focal plane, such as a zoom lens.
In the past where it has been desired to alter focal length, this has usually been accomplished by continuously or discretely changing the length of the optical system, or by changing the location or type of imaging lenses in the front or rear, or in both front and rear optical systems. Altering focal length without utilizing the imaging lens system, or changing the length of the optical system, or changing the location or type of lenses in either the front or rear optical system has not been known in the prior art.
In the known prior art, Hillman U.S. Pat. No. 2,937,570 discloses a telescope system in which the image forming lenses are moved in order to focus the system. That is, focusing is accomplished by moving objective lens and focusing lens, which are part of the telescope's "formula-specific" objective imaging system. Focusing is not accomplished or taught to be feasible by moving a portion of an afocal variator, nor by moving a portion of any other non-image forming modular optical lens system. Furthermore, this reference discloses a "formula-specific" optical system in which the lenses are all calculated and assembled to work together to form a telescope. It does not include an independent optical lens system module which is non-image forming. It does not include a central afocal variator module which does not comprise a portion of the image-forming optics. If any of the movable lenses of any of the systems taught by Hillman were removed, the entire system would be affected, very probably to the point that the system would no longer function for its intended purpose.
Quenderff French Patent No. 2,572,545 the use of a zoom lens to make enlarged pictures, and also teaches the use of various art known mechanical devices for connecting together optical modules. However, it neither teaches nor suggests the use of a central afocal variator module as a focusing element.